Changes in Water Quality Parameters in Different Processes of Surface Water Treatment Plant (Case study: Tehranpars Water Treatment Plant)

  Background and purpose: Water treatment is of great importance in human life, due to the contamination of water resources. Therefore, continuous evaluation of the performance of water treatment plants is necessary to minimize contamination within the treatment plant in order to create optimal conditions. Materials and methods: A cross-sectional descriptive analytic study was performed in Tehranpars water treatment plant. Water samples were collected at different stages (Pre-chlorination, Pulsator, Filtration and Post-chlorination) during 30 months. The samples were randomly taken one day per week and pH, water temperature, turbidity, dissolved organic carbon (DOC), and chlorophyll a contents were measured. Results: Average turbidity removal in pre-chlorination, pulsator, filtration, and final chlorination units were approximately (9%±1.74), (39%±0.77), (44% ±0.23), and (4%±0.1.74), respectively and the overall efficiency of the treatment plant was 96%. The mean concentrations of DOC in effluent of Tehranpars water treatment plant were 2.37±0.16, 2.94±0.32, 1.74±0.07, and 2.17±0.16 mg/L in spring, summer, fall, and winter, respectively. Mean DOC values were higher than limits (2 mg/L) in all seasons except fall. Chlorophyll a concentrations in water entering the treatment plant were higher in summer and spring than other two seasons. Conclusion: Tehranpars water treatment plant showed considerable efficiency in reducing water turbidity. Pre-chlorination and final chlorination processes had the greatest effect on minimizing DOC concentration due to the high affinity of organic compounds with chlorine and formation of disinfectant by-products. Therefore, pre-ozonation is recommended as a solution to reduce the production of these hazardous organic compounds rather than pre-chlorination.